Commercial and industrial buildings require ventilation, and it is common for the natural leakage around doors, wall-ceiling joints, etc. found in standard building construction to allow sufficient ventilation air to enter the building. A pressure drop from the exterior to the interior of the building can arise from many factors, such as high winds, exhaust fans and combustion air for fuel-burning furnaces. This tends to draw outside air into the building through any crack or opening.
The problem with the conventional approach is that the amount of ventilation air is not controlled, and additional heat must be provided to heat the outside air to room temperature during the fall, winter and spring months.
This problem has typically been solved by installing air make-up fans with gas or electric heaters to heat the incoming air. When solar panels are used to heat a building, air is re-circulated from the building through the panels and then back again to the building. The efficiency of a solar collector is maximized when the temperature of the air entering the collector is the same as the ambient temperature. Under normal winter conditions, the ambient temperature is lower than the room temperature, and therefore a recirculating solar collector operates at a much reduced efficiency level in wintertime.
My own earlier Canadian Pat. No. 1,196,825, issued Nov. 19, 1985 and entitled "Method for Preheating Ventilation Air in a Building" describes a method and apparatus which avoid using consumable energy sources like gas or electricity to heat incoming air for a building, and instead of simply recirculating interior air from the building through a solar collector and back to the building, it introduces fresh make-up air for ventilation purposes into the interior of the building after first passing the air through a solar collector located on a south-facing wall of the building. The solar collector in my earlier patent consists of glazing over a darkened wall. Air moving means, such as a fan and duct arrangement, is used to gather air at the top of the solar collector and force it into the building.